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BIG PHYSICS, BIG QUESTIONS –

Pasta spirals link neutron stars and the machinery of your cells

Barbara Mocellin / EyeEm/Getty

By Leah Crane

The conditions are vastly different, but the pasta is the same. The insides of neutron stars and the membranes inside our cells can form strikingly similar structures resembling cavatappi pasta spirals, which could forge a new link between the cosmos and life on Earth.

Neutron stars are the ultra-dense cores left behind after a stellar explosion. They are thought to have a liquid core of free neutrons beneath a solid crust, in which protons, neutrons and electrons clump together under competing attractive and repulsive forces.

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Simulations had shown that those forces can make the crustal material arrange itself into a dense layer of “nuclear pasta” shapes, sometimes taking the form of lasagna-like sheets connected by spiral bridges.

Now, Matt Caplan at Indiana University Bloomington and his colleagues have pointed out that the same patterns show up inside cells. Despite the fact that neutron stars are 14 orders of magnitude denser than the constituents of cells, the forces in both interact in a similar way, making the resulting self-assembling shapes nearly identical.

Lucky coincidence

This parallel came to light through a lucky coincidence. Biophysicist Greg Huber of the Kavli Institute for Theoretical Physics in Santa Barbara, California, happened to see a photograph from a conference talk given by Caplan, depicting a spiral bridge structure.

Huber noticed the similarity between nuclear pasta and the endoplasmic reticulum, a network of membranes found in many cells that is responsible for folding proteins. He wrote to Caplan’s team to point out the coincidence, and they teamed up to compare new simulations of nuclear pasta with observations of cells.

The team suggest that the similarities point to a deeper connection between stars and cells, and provide a way for the two fields to share insights.

“Self-assembly is universal,” says Caplan. “It lets us bridge a gap between two fields, because we can take the language of biophysics and use it to understand neutron star interiors, and the biophysicists can take computational methods from astrophysics.”

In the cell, the bridges may help membranes remain parallel and connected, yielding more space for ribosomes, which sit on the endoplasmic reticulum’s surface and build proteins. In a neutron star, on the other hand, the spiral bridges that link dense sheets of particles scatter electrons and slow the neutron star’s cooling. So the very structures that keep neutron stars warm could help our bodies produce vital proteins.

“It was interesting to see that there is more evidence that some mechanisms in biological systems and nuclear astrophysics are similar,” says Bastian Schütrumpf at Michigan State University, who has studied structures called gyroids that show up in both neutron star crusts and butterfly wings.

But for Huber, the fact that these shapes arise in such different environments points to a larger puzzle. “It’s the enduring mystery of what we found, that these two very different systems have these very deep similarities,” Huber says. “To me the important part is the questions that are raised.”